Determination of amount of proppant added to a fracture fluid using a coriolis flow meter

ABSTRACT

A measurement system ( 200 ) is disclosed comprising a Coriolis flow meter ( 222 ) and a control system ( 224 ). A base fluid ( 250 ) is first flowed through the Coriolis flow meter. The Coriolis flow meter measures a density of the base fluid and transmits a base fluid density measurement to the control system. A proppant ( 252 ) is then added to the base fluid to create a fracture fluid ( 202 ). The fracture fluid is then flowed through the Coriolis flow meter. The Coriolis flow meter measures a density of the fracture fluid and transmits a fracture fluid density measurement to the control system. The control system determines an amount of proppant in the fracture fluid based on the base fluid density measurement, the fracture fluid density measurement, and a density of the proppant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is related to the field of measurement systems, and inparticular, to a system and method that use measurements from a Coriolisflow meter to determine the amount of proppant in a fracture fluid.

2. Statement of the Problem

Oil, gas, and other resources under ground are obtained by drilling awell. The well is drilled to a certain depth and cased in cement. Thewell extends through multiple zones in the ground that a drilling crewmay wish to tap. To tap into a certain zone, the drilling crew fracturesa portion of the casing in the desired zone. The fracturing process usedcould be hydraulic fracturing, pneumatic fracturing, or another type offracturing. With the casing fractured, the drilling crew then pumps afracture fluid into the fracture to keep the fracture open. The fracturefluid holds the fracture open while still being permeable. This enablesthe oil and gas to more easily flow through the fracture into thewell-bore.

The fracture fluid is made up of a base fluid and a proppant. To makethe base fluid, a Guar gum is added to water in a large tank. A mixerwithin the tank continually mixes the Guar gum and the water together tomake the base fluid. When mixed, the base fluid has the consistencysomewhat like molasses.

A proppant, such as sand, is then added to the base fluid in the tank tomake the fracture fluid. The amount of sand added depends on soil type,soil conditions, and other factors. The mixer in the tank mixes the basefluid and the sand together to make the fracture fluid. The fracturefluid is then pumped into the well-bore to help keep the fracture open.The amount of the sand in the fracture fluid determines how well thefracture fluid is able to hold the fracture open.

Because the amount of sand in the fracture fluid is important, thedrilling crew may want to measure the amount of sand added. This can bea difficult process because the fracture fluid is usually not made in abatch, but is continuously mixed. To determine the amount of sand in thefracture fluid, the drilling crew uses a nuclear densitometer to measurethe density of the fracture fluid being pumped into the well-bore. Acontroller receives the density measurement from the nucleardensitometer and calculates the amount of sand added to the fracturefluid. The drilling crew can then adjust the amount of sand to a desiredlevel. An example of a system for providing the fracture fluid isdescribed below and illustrated in FIG. 1.

Unfortunately, there are problems associated with using nucleardensitometers. For instance, interstate and international transport ofnuclear densitometers can be a difficult process considering the lawsand regulations surrounding nuclear technology. There are also concernsfor safe handling and transporting of the nuclear densitometers. Theoperators of the nuclear densitometers have to be certified or licensedby the proper regulatory agency. Such factors make nuclear densitometersundesirable to use.

Coriolis flow meters are used to measure the mass flow rate, density,and other information for fluids. Exemplary Coriolis flow meters aredisclosed in U.S. Pat. No. 4,109,524 of Aug. 29, 1978, U.S. Pat. No.4,491,025 of Jan. 1, 1985, and Re. 31,450 of Feb. 11, 1982, all to J. E.Smith et al. Coriolis flow meters are comprised of one or more flowtubes of a straight or curved configuration. Each flow tubeconfiguration in a Coriolis flow meter has a set of natural modes ofvibration, which may be of a simple bending, twisting, torsional, orcoupled type. Each flow tube is driven to oscillate at resonance in oneof these natural modes of vibration. Fluid flows into the flow meterfrom a connected pipeline on the inlet side of the flow meter. The fluidis directed through the flow tube(s), and exits the flow meter throughthe outlet side of the flow meter. The natural vibration modes of thevibrating, fluid-filled system are defined in part by the combined massof the flow tubes and the mass of the fluid flowing through the flowtubes.

As fluid begins to flow through the flow tubes, Coriolis forces causepoints along the flow tubes to have a different phase. The phase on theinlet side of the flow tube commonly lags the driver while the phase onthe outlet side of the flow tube leads the driver. Pickoffs are affixedto the flow tube(s) to measure the motion of the flow tube(s) andgenerate pickoff signals that are representative of the motion of theflow tube(s).

Meter electronics, or any other ancillary electronics or circuitryconnected to the flow meter, receive the pickoff signals. The meterelectronics processes the pickoff signals to determine the phasedifference between the pickoff signals. The phase difference between twopickoff signals is proportional to the mass flow rate of the fluidthrough the flow tube(s). The meter electronics can also process one orboth of the pickoff signals to determine the density of the fluid.

Unfortunately, Coriolis flow meters have not been used to measure thedensity of a fracture fluid. First, the fracture fluid is usually pumpeddown the well-bore through a large tube, such as an eight inch tube.Coriolis flow meters have not been built large enough to measure aneight inch stream. Secondly, most Coriolis flow meters have curved flowtubes. The erosive properties of sand through the curved flow tubesprevents the curved-tube Coriolis flow meter from being a viable option.The sand would damage the flow tubes in a matter of hours. For thesereasons, Coriolis flow meters have not been used to measure the fracturefluid, and nuclear densitometers continue to be used.

SUMMARY OF THE SOLUTION

The invention helps solve the above problems with a measurement systemcomprising a Coriolis flow meter and a control system. A base fluid isfirst flowed through the Coriolis flow meter. The Coriolis flow metermeasures a density of the base fluid and transmits a base fluid densitymeasurement to the control system. A proppant is added to the base fluidcreating a fracture fluid. The fracture fluid is then flowed through theCoriolis flow meter. The Coriolis flow meter measures a density of thefracture fluid and transmits a fracture fluid density measurement to thecontrol system. The control system determines an amount of proppant inthe fracture fluid based on the base fluid density measurement, thefracture fluid density measurement, and a density of the proppant.

The measurement system advantageously replaces nuclear technology withCoriolis technology. Coriolis flow meters can provide accurate densitymeasurements, while avoiding the problems of handling and transportingradioactive sources and instruments. Coriolis flow meters also do nothave the intrinsic safety concerns of the nuclear densitometer.

In another example of the invention, the Coriolis flow meter isconfigured to receive a slip stream of material. To provide the slipstream, the measurement system further comprises a first tube and asecond tube. The first tube has a first end configured to connect to aninput of the Coriolis flow meter and has a second end configured toconnect to a discharge of a tank. The second tube has a first endconfigured to connect to an output of the Coriolis flow meter and has asecond end configured to connect to a tank. The first tube receives aslip stream of material from the discharge of the tank. The slip streamtravels through said first tube, through said Coriolis flow meter,through said second tube, and back into said tank. The slip streamadvantageously provides a smaller flow to measure, such as a one inchflow.

Other examples of the invention may be disclosed below.

The following sets forth aspects of the invention. One aspect of theinvention comprises a measurement system comprising a Coriolis flowmeter and a control system,

said measurement system characterized by:

-   -   said Coriolis flow meter being configured to measure a density        of a base fluid (250) flowing through said Coriolis flow meter        to generate a base fluid density measurement, transmit said base        fluid density measurement, measure a density of a fracture fluid        (202) flowing through said Coriolis flow meter to generate a        fracture fluid density measurement, wherein said fracture fluid        comprises a mixture of said base fluid and a proppant (252), and        transmit said fracture fluid density measurement; and    -   said control system being configured to receive said base fluid        density measurement and said fracture fluid density measurement,        and determine an amount of said proppant in said fracture fluid        based on said base fluid density measurement, said fracture        fluid density measurement, and a density of said proppant.

Preferably, the Coriolis flow meter comprises a straight tube Coriolisflow meter.

Preferably, the Coriolis flow meter is configured to receive a slipstream of said fracture fluid to measure said density of said fracturefluid.

Preferably, the measurement system further comprises:

a first tube having a first end configured to connect to an input ofsaid Coriolis flow meter and having a second end configured to connectto a discharge of a tank; and

a second tube having a first end configured to connect to an output ofsaid Coriolis flow meter and having a second end configured to connectto said tank;

wherein said first tube is configured to receive a slip stream ofmaterial from said discharge of said tank, said slip stream travelsthrough said first tube, through said Coriolis flow meter, through saidsecond tube, and back into said tank.

Preferably, the control system is configured to determine said densityof said proppant.

Preferably, the control system comprises a display system configured toprovide said amount of said proppant to a user.

Preferably, the control system comprises an auxiliary interfaceconfigured to transmit a signal representing said amount of saidproppant to an auxiliary system.

Preferably, the control system comprises a user interface configured toreceive said density of said proppant entered by a user.

Preferably, the control system is configured to:

calculate a velocity of said fracture fluid;

determine if said velocity of said fracture fluid exceeds a threshold;and

provide an indication if said velocity of said fracture fluid exceedssaid threshold.

Preferably, the control system is configured to:

calculate an average density of said base fluid based on a plurality ofdensity measurements of said base fluid by said Coriolis flow meter; and

determine said amount of said proppant in said fracture fluid based onsaid average density of said base fluid, said fracture fluid densitymeasurement, and said density of said proppant.

Preferably, the Coriolis flow meter is configured to measure a mass flowrate of said fracture fluid, and provide at least one of said mass flowrate of said fracture fluid and a drive gain of said Coriolis flow meterto said control system; and

said control system is configured to provide at least one of said massflow rate of said fracture fluid and said drive gain of said Coriolisflow meter to a user.

Another aspect of the invention comprises a method of measuring anamount of proppant in a fracture fluid, said method comprising the stepof:

determining a density of said proppant;

said method characterized by the steps of:

-   -   measuring a density of a base fluid with a Coriolis flow meter        to generate a base fluid density measurement;    -   measuring a density of a fracture fluid with said Coriolis flow        meter to generate a fracture fluid density measurement, wherein        said fracture fluid comprises a mixture of said base fluid and a        proppant; and    -   determining an amount of said proppant in said fracture fluid        based on said base fluid density measurement, said fracture        fluid density measurement, and said density of said proppant.

Preferably, the step of measuring a density of a fracture fluid withsaid Coriolis flow meter comprises:

measuring said density of said fracture fluid with a straight tubeCoriolis flow meter.

Preferably, the step of measuring a density of a fracture fluid withsaid Coriolis flow meter comprises:

receiving a slip stream of said fracture fluid into said Coriolis flowmeter to measure said density of said fracture fluid.

Preferably, the method further comprises the steps of:

connecting a first end of a first tube to an input of said Coriolis flowmeter;

connecting a second end of said first tube to a discharge of a tank;

connecting a first end of a second tube to an output of said Coriolisflow meter; and

connecting a second end of said second tube to said tank;

wherein said first tube receives a slip stream of material from saiddischarge of said tank, said slip stream travels through said firsttube, through said Coriolis flow meter, through said second tube, andback into said tank.

Preferably, the method further comprises the step of providing saidamount of said proppant to a user.

Preferably, the method further comprises the step of transmitting asignal representing said amount of said proppant to an auxiliary system.

Preferably, the method further comprises the step of receiving saiddensity of said proppant from a user.

Preferably, the method further comprises the steps of:

calculating a velocity of said fracture fluid;

determining if said velocity of said fracture fluid exceeds a threshold;and

providing an indication if said velocity of said fracture fluid exceedssaid threshold.

Preferably, the method further comprises the steps of:

calculating an average density of said base fluid based on a pluralityof density measurements of said base fluid by said Coriolis flow meter;and

determining said amount of said proppant in said fracture fluid based onsaid average density of said base fluid, said fracture fluid densitymeasurement, and said density of said proppant.

Preferably, the method further comprises the steps of:

measuring a mass flow rate of said fracture fluid with said Coriolisflow meter; and

providing at least one of said mass flow rate of said fracture fluid anda drive gain of said Coriolis flow meter to a user.

DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings.

FIG. 1 illustrates a system for supplying a fracture fluid to awell-bore in the prior art.

FIG. 2 illustrates a measurement system in an example of the invention.

FIG. 3 illustrates an example of a control system in an example of theinvention.

FIG. 4 illustrates an example of a Coriolis flow meter in an example ofthe invention.

FIG. 5 is a flow chart illustrating an example operation of ameasurement system in an example of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a system for supplying a fracture fluid to awell-bore in the prior art to assist in understanding the invention.FIGS. 2-5 and the following description depict specific examples of theinvention to teach those skilled in the art how to make and use the bestmode of the invention. For the purpose of teaching inventive principles,some conventional aspects of the invention have been simplified oromitted. Those skilled in the art will appreciate variations from theseexamples that fall within the scope of the invention. Those skilled inthe art will appreciate that the features described below can becombined in various ways to form multiple variations of the invention.As a result, the invention is not limited to the specific examplesdescribed below, but only by the claims and their equivalents.

System for Supplying a Fracture Fluid in the Prior Art—FIG. 1

FIG. 1 illustrates a fracture fluid system 100 for supplying a fracturefluid 102 to a well-bore in the prior art. Fracture fluid system 100 iscomprised of a tank/mixer 110, a recirculation tube 111, a supply tube112, a discharge tube 118, a valve 113, a pump 128, a nucleardensitometer 114, and a controller 116. Discharge tube 118 is connectedto tank/mixer 110 at one end and valve 113 at the other. Pump 128 andnuclear densitometer 114 are connected to discharge tube 118.Recirculation tube 111 is connected to valve 113 at one end andtank/mixer 110 at the other. Supply tube 112 is connected to valve 113and is configured to transport the fracture fluid 102 to the well-bore.Valve 113 either directs a flow of the fracture fluid 102 throughrecirculation tube 111 or through supply tube 112. Supply tube 112,recirculation tube 111, and discharge tube 118 have at least eight inchdiameters. Controller 116 is coupled to nuclear densitometer 114.

In operation, water 120, gum 122, and sand 124 are added to tank/mixer110. Tank/mixer 110 mixes the water 120, the gum 122, and the sand 124together to make the fracture fluid 102. The amount of sand added to thewater 120 and the gum 122 in the fracture fluid 102 depends on the soiltype, soil conditions, and other factors. The operator of fracture fluidsystem 100 uses nuclear densitometer 114 and controller 116 to measurethe amount of sand in the fracture fluid 102.

As the full stream of the fracture fluid 102 flows through dischargetube 118, nuclear densitometer 114 measures the density of the fracturefluid 102. Nuclear densitometer 114 transmits the density measurement tocontroller 116. Controller 116 knows the density of the sand 124, thedensity of the water 120, and the density of the gum 122. These valuesmay be entered into controller 116 by the operator. Controller 116calculates the amount of sand in the fracture fluid 102 based on thedensity measurement of the fracture fluid 102, and the known densitiesof the sand 124, the water 120, and the gum 122. Controller 116 includesa display 136. Controller 116 provides the amount of sand in thefracture fluid 102 to the operator using display 136.

As described above, there are many problems associated with usingnuclear densitometer 114. For instance, interstate and internationaltransport of nuclear densitometers can be a difficult process, safehandling and transporting of the nuclear densitometers is a concern, andthe people operating the nuclear densitometers have to be certified orlicensed by the proper regulatory agency. Such factors make nucleardensitometers undesirable to use.

Measurement System and Operation—FIG. 2

FIG. 2 illustrates a measurement system 200 in an example of theinvention. Measurement system 200 is configured to operate with afracture fluid system 201 for supplying a fracture fluid 202 to awell-bore (not shown). Fracture fluid system 201 is comprised of atank/mixer 210, a discharge tube 218, a valve 213, a recirculation tube211, a supply tube 212, a pump 228, and measurement system 200.Discharge tube 218 is connected to tank/mixer 210 at one end and valve213 at the other. Pump 228 is also connected to discharge tube 218.Recirculation tube 211 is connected to valve 213 at one end andtank/mixer 210 at the other. Supply tube 212 is connected to valve 213and is configured to transport the fracture fluid 202 to the well-bore.Valve 213 either directs a flow of material through recirculation tube211 or through supply tube 212. Fracture fluid system 201 may becomprised of many other components that are not shown for the sake ofbrevity.

Measurement system 200 is comprised of a Coriolis flow meter 222 and acontrol system 224. Measurement system 200 may also include tubes226-227 that form a slip stream from discharge tube 218. Tubes 226-227may be one inch rubber tubing. Tube 226 includes ends 271 and 272. End271 connects to an inlet end of Coriolis flow meter 222. End 272connects to discharge tube 218. End 272 may connect to an elbow ofdischarge tube 218 to obtain the best results. Tube 227 includes ends281 and 282. End 281 connects to an outlet end of Coriolis flow meter222 and end 282 connects to tank/mixer 210. Tube 226, Coriolis flowmeter 222, and tube 227 are configured to receive a slip stream 280 ofmaterial. The slip stream 280 enters tube 226, and passes through tube226, through Coriolis flow meter 222, through tube 227, and back intotank/mixer 210.

The following definitions may be helpful in understanding the invention.A Coriolis flow meter comprises any meter configured to measure adensity of a material based on the Coriolis principle. An example of aCoriolis flow meter is a Model T-100 straight tube meter manufactured byMicro Motion Inc. of Boulder, Colo. A fracture fluid comprises anyfluid, material, or mixture used to resist crushing of a fracture in awell-bore and provide a permeable path. A proppant comprises anymaterial or agent used in a fracture fluid to help keep the fracturesopen. An example of a proppant is sand. A base fluid comprises anymaterial or agent mixed with a proppant to form a fracture fluid. A tankor tank/mixer comprises any tub or container that stores a material. Atube comprises any hose, tubing, line, pipe, etc.

In operation, tank/mixer 210 receives and mixes the base fluid 250.Based on the setting of valve 213, pump 228 circulates the base fluid250 through discharge tube 218 and recirculation tube 211. Tube 226receives a slip stream 280 of the base fluid 250. The slip stream 280 ofthe base fluid 250 travels through tube 226, through Coriolis flow meter222, through tube 227, and back into tank/mixer 210. With the base fluid250 flowing through Coriolis flow meter 222, Coriolis flow meter 222measures a density of the base fluid 250. Coriolis flow meter 222transmits a base fluid density measurement to control system 224.

Tank/mixer 210 then receives and mixes the proppant 252 with the basefluid 250 to make the fracture fluid 202. Based on the setting of valve213, pump 228 circulates the fracture fluid 202 through discharge tube218 and recirculation tube 211. Tube 226 receives a slip stream 280 ofthe fracture fluid 202. The slip stream 280 of the fracture fluid 202travels through tube 226, through Coriolis flow meter 222, through tube227, and back into tank/mixer 210. With the fracture fluid 202 flowingthrough Coriolis flow meter 222, Coriolis flow meter 222 measures adensity of the fracture fluid 202. Coriolis flow meter 222 transmits afracture fluid density measurement to control system 224.

Control system 224 receives the base fluid density measurement and thefracture fluid density measurement. Control system 224 also receives thedensity of the proppant 252. Control system 224 may receive the densityof the proppant 252 from an operator, from a memory, or from anothersource. Control system 224 determines an amount of the proppant 252 inthe fracture fluid 202 based on the base fluid density measurement, thefracture fluid density measurement, and the density of the proppant 252.An operator of fracture fluid system 201 can look at the amount ofproppant 252 in the fracture fluid 202, as determined by control system224, to adjust the amount of the proppant 252 added to the fracturefluid 202. Based on this disclosure, those skilled in the art willappreciate how to modify existing measurement systems to makemeasurement system 200.

When the fracture fluid 202 has the proper amount of proppant 252, valve213 is switched so that the fracture fluid 202 is pumped down holethrough supply tube 212. There maybe other devices or systems connectedto supply tube 212 to pump the fracture fluid 202 down hole, such as alarge pump.

Control System—FIG. 3

FIG. 3 illustrates an example of control system 224 in an example of theinvention. Control system 224 comprises a display 302, a user interface304, and an auxiliary interface 306. An example of control system 224 isthe Daniel™ FloBoss™ 407. Display 302 is configured to display anyrelevant data to an operator. An example of display 302 is a LiquidCrystal Display (LCD). User interface 304 is configured to allow theoperator to enter information into control system 224. An example ofuser interface 304 is a keypad. Auxiliary interface 306 is configured totransmit information to, and receive information from, an auxiliarysystem (not shown). An example of auxiliary interface 306 is a serialdata port.

Control system 224 may also comprise a processor and a storage media.The operation of control system 224 may be controlled by instructionsthat are stored on the storage media. The instructions can be retrievedand executed by the processor. Some examples of instructions aresoftware, program code, and firmware. Some examples of storage media arememory devices, tape, disks, integrated circuits, and servers. Theinstructions are operational when executed by the processor to directthe processor to operate in accord with the invention. The term“processor” refers to a single processing device or a group ofinter-operational processing devices. Some examples of processors arecomputers, integrated circuits, and logic circuitry. Those skilled inthe art are familiar with instructions, processors, and storage media

Coriolis Flow Meter—FIG. 4

FIG. 4 illustrates an example of a Coriolis flow meter 400 in an exampleof the invention. Coriolis flow meter 400 could be Coriolis flow meter222 illustrated in FIG. 2. Coriolis flow meter 400 comprises a Coriolissensor 402 and meter electronics 404. Meter electronics 404 is connectedto Coriolis sensor 402 via paths 406. Meter electronics 404 isconfigured to provide density, mass flow rate, volumetric flow rate,totalized mass flow, and other information over path 408.

Coriolis sensor 402 comprises a flow tube 410, a balance bar 412,process connections 414-415, a driver 422, pickoffs 424-425, and atemperature sensor 426. Flow tube 410 includes a left end portiondesignated 410L and a right end portion designated 41 OR. Flow tube 410and its ends portions 410L and 410R extend the entire length of Coriolissensor 402 from an input end of flow tube 410 to an output end of flowtube 410. Balance bar 412 is connected at its ends to flow tube 410 bybrace bar 416.

Left end portion 410L is affixed to inlet process connection 414. Rightend portion 410R is affixed to outlet process connection 415. Inletprocess connection 414 and outlet process connection 415 are configuredto connect Coriolis sensor 402 to a pipeline (not shown).

In a conventional manner, driver 422, left pickoff 424, and rightpickoff 425 are coupled to flow tube 410 and balance bar 412. Meterelectronics 404 transmits a driver signal to driver 422 over path 432.Responsive to the driver signal, driver 422 vibrates flow tube 410 andbalance bar 412 in phase opposition at the resonant frequency of thefluid-filled flow tube 410. The oscillation of vibrating flow tube 410induces Coriolis deflections in the flow tube 410 in a well knownmanner. The pickoffs 424 and 425 detect the Coriolis deflections andtransmit pickoff signals that represent the Coriolis deflections overpaths 434 and 435, respectively.

Temperature sensor 426 is connected to flow tube 410. Temperature sensor426 detects the temperature of the fluid flowing through flow tube 410.Temperature sensor 426 generates a temperature signal, and transmits thetemperature signal to meter electronics 404 over path 436.

Example Operation of Measurement System—FIG. 5

FIG. 5 is a flow chart illustrating an example method 500 of operationof measurement system 200 in an example of the invention. An operatorturns on control system 224 and Coriolis flow meter 222. Control system224 receives an instruction to clear the memory on control system 224.The operator clears the memory by entering a “Clear” instruction throughuser interface 304. In step 504, control system 224 prompts the operatorto enter a density of the proppant 252. Control system 224 prompts theoperator by displaying “Enter Density of Proppant” through display 302.The operator enters the density of the proppant 252, in pounds pergallon, through user interface 304. Assume for this example that theproppant 252 is sand having a density of 22.1 lbs/gal. In step 506,control system 224 receives the density of the proppant 252 as enteredby the operator. The density of the proppant may also be retrieved frommemory, or received from another system.

Tank/mixer 210 mixes the base fluid 250 without the proppant 252. Basedon the setting of valve 213, pump 228 circulates the base fluid 250through discharge tube 218 and recirculation tube 211. Tube 226 receivesa slip stream 280 of the base fluid 250. The slip stream 280 of the basefluid 250 travels through tube 226, through Coriolis flow meter 222,through tube 227, and back into tank/mixer 210. With the base fluid 250flowing through Coriolis flow meter 222, Coriolis flow meter 222measures a density of the base fluid 250 in step 508. Coriolis flowmeter 222 transmits a base fluid density measurement to control system224. Control system 224 displays the base fluid density measurement tothe operator in step 510. Coriolis flow meter 222 may also measure amass flow rate of the base fluid 250, a temperature of the base fluid250, and other parameters in step 508. Control system 224 may alsodisplay the mass flow rate, the temperature, and the other parameters tothe operator in step 510. The operator could scroll through thedifferent parameters to view a desired parameter.

In step 512, control system 224 calculates an average density of thebase fluid 250. Control system 224 calculates the average density bytaking the average of ten density measurements of the base fluid 250.Control system 224 may also calculate the average density by taking theaverage of the density measurements over a five second interval. Whilecalculating the average density, control system 224 may display“Stabilizing on Base Fluid” to the operator. Control system 224 maycalculate the average density responsive to an instruction from theoperator. For instance, the operator watches the density measurement andthe temperature measurement displayed by control system 224 to see ifthe measurements stabilize. If the measurements stabilize, then theoperator instructs control system 224 to calculate the average density.

In step 514, control system 224 determines whether the average densityjust calculated is stable. For instance, if the average density variedby more than 1% within a five second interval, then the average densityis not stable. In that case, control system 224 displays “UnstableDensity” to the operator and returns to step 512. If the average densitydid not vary by more than 1%, then the average density is stable and canbe used. Control system 224 displays the stable average density of thebase fluid 250 to the operator in step 516.

At this point, tank/mixer 210 mixes the proppant 252 into the base fluid250 to make the fracture fluid 202. Based on the setting of valve 213,pump 228 circulates the fracture fluid 202 through discharge tube 218and recirculation tube 211. Pump 228 re-circulates the fracture fluid tocontinuously blend the fracture fluid 202 to the proper specifications.Tube 226 receives a slip stream 280 of the fracture fluid 202. The slipstream 280 of the fracture fluid 202 travels through tube 226, throughCoriolis flow meter 222, through tube 227, and back into tank/mixer 210.With the fracture fluid 202 flowing through Coriolis flow meter 222,Coriolis flow meter 222 measures a density of the fracture fluid 202 instep 518. Coriolis flow meter 222 transmits a fracture fluid densitymeasurement to control system 224.

Control system 224 then calculates the pounds of sand added to thefracture fluid 202. To calculate the pounds of sand added, controlsystem 224 uses the following equations. In step 520, control system 224calculates the percentage of solids (%S) in the fracture fluid 202 usingequation 1.% S=(ρ_(frac fluid)−ρ_(base fluid))/(ρ_(proppant)−ρ_(base fluid))   [1]where ρ_(frac fluid) is the density of the fracture fluid 202,ρ_(base fluid) is the density of the base fluid 250, and ρ_(proppant) isthe density of the proppant 252.

In step 522, control system 224 calculates the proppant displacement(P.D.) using equation 2.P.D.=231/ρ_(proppant)   [2]where ρ_(proppant) is the density of the proppant 252.

In step 524, control system 224 calculates the pounds of sand added(P.S.A.) to the fracture fluid 202 using equation 3.P.S.A.=(%S*231)/((1−%S)* P.D.)   [3]The pounds of sand added (P.S.A.) may also be referred to as pounds ofproppant added (P.P.A.).

Control system 224 may calculate the pounds of sand added using equation4 instead of equations 1-3.P.S.A.=(ρ_(frac fluid)−ρ_(base fluid))/((1−(ρ_(frac fluid)/ρ_(proppant)))  [4]where ρ_(frac fluid) is the density of the fracture fluid 202,ρ_(base fluid) is the density of the base fluid 250, and ρ_(proppant) isthe density of the proppant 252.

In step 526, control system 224 displays the pounds of sand added to thefracture fluid 202. Control system 224 displays the pounds of sand addedin units of pounds of sand added per one gallon of water. Control system224 also generates a signal representing the pounds of sand added. Thesignal may be a 4-20 mA signal for an auxiliary system (not shown).Coriolis flow meter 222 may also measure a mass flow rate of thefracture fluid 202, a temperature of the fracture fluid 202, and otherparameters in step 518. Control system 224 may display the mass flowrate, the temperature, and the other parameters to the operator in step526. The operator could scroll through the different parameters to viewa desired parameter. Control system 224 returns to step 518.

Method 500 may further include steps 528 and 530. In step 528, controlsystem 224 compares the velocity of the fracture fluid 202 to athreshold value. Control system 224 calculates the velocity (velocity_(material)) of the fracture fluid 202 using equation 5.velocity_(material)=flow rate_(material)*A.F.   [5]where A.F. is an area factor and flow rate _(material) is the flow rateof the material. The area factor (A.F.) may be received from theoperator or retrieved from a memory or other system. If the velocity ofthe fracture fluid 202 exceeds the threshold value, then control system224 provides an indication that the velocity exceeds the threshold valuein step 530. For instance, if the velocity of the fracture fluid 202exceeds 12 ft/sec, then control system 224 triggers an alarm. If thevelocity of the fracture fluid 202 does not exceed the threshold value,then control system 224 returns to step 518.

Control system 224 continues to calculate the pounds of sand added tothe fracture fluid 202. Tank/mixer 210 is a continuous mixing system,not a batch system. Therefore, the operator has control system 224measure the pounds of sand added as long as tank/mixer 210 is providingthe fracture fluid 202 to the well-bore.

1. A measurement system comprising a Coriolis flow meter and a controlsystem, said measurement system characterized by: said Coriolis flowmeter being configured to measure a density of a base fluid flowingthrough said Coriolis flow meter to generate a base fluid densitymeasurement, transmit said base fluid density measurement, measure adensity of a fracture fluid flowing through said Coriolis flow meter togenerate a fracture fluid density measurement, wherein said fracturefluid comprises a mixture of said base fluid and a proppant, andtransmit said fracture fluid density measurement; and said controlsystem being configured to receive said base fluid density measurementand said fracture fluid density measurement, and determine an amount ofsaid proppant in said fracture fluid based on said base fluid densitymeasurement, said fracture fluid density measurement, and a density ofsaid proppant.
 2. The measurement system of claim 1 wherein saidCoriolis flow meter comprises a straight tube Coriolis flow meter. 3.The measurement system of claim 1 wherein said Coriolis flow meter isconfigured to receive a slip stream of said fracture fluid to measuresaid density of said fracture fluid.
 4. The measurement system of claim1 further comprising: a first tube having a first end configured toconnect to an input of said Coriolis flow meter and having a second endconfigured to connect to a discharge of a tank; and a second tube havinga first end configured to connect to an output of said Coriolis flowmeter and having a second end configured to connect to said tank;wherein said first tube is configured to receive a slip stream ofmaterial from said discharge of said tank, said slip stream travelsthrough said first tube, through said Coriolis flow meter, through saidsecond tube, and back into said tank.
 5. The measurement system of claim1 wherein said control system is configured to determine said density ofsaid proppant.
 6. The measurement system of claim 1 wherein said controlsystem comprises: a display system configured to provide said amount ofsaid proppant to a user.
 7. The measurement system of claim 1 whereinsaid control system comprises: an auxiliary interface configured totransmit a signal representing said amount of said proppant to anauxiliary system.
 8. The measurement system of claim 1 wherein saidcontrol system comprises: a user interface configured to receive saiddensity of said proppant entered by a user.
 9. The measurement system ofclaim 1 wherein said control system is configured to: calculate avelocity of said fracture fluid; determine if said velocity of saidfracture fluid exceeds a threshold; and provide an indication if saidvelocity of said fracture fluid exceeds said threshold.
 10. Themeasurement system of claim 1 wherein said control system is configuredto: calculate an avenge density of said base fluid based on a pluralityof density measurements of said base fluid by said Coriolis flow meter;and determine said amount of said proppant in said fracture fluid basedon said average density of said base fluid, said fracture fluid densitymeasurement, and said density of said proppant.
 11. The measurementsystem of claim 1 wherein: said Coriolis flow meter is configured tomeasure a mass flow rate of said fracture fluid, and provide at leastone of said mass flow rate of said fracture fluid and a drive gain ofsaid Coriolis flow meter to said control system; and said control systemis configured to provide at least one of said mass flow rate of saidfracture fluid and said drive gain of said Coriolis flow meter to auser.
 12. A method of measuring an amount of proppant in a fracturefluid, said method comprising the step of: determining a density of saidproppant; said method characterized by the steps of: measuring a densityof a base fluid with a Coriolis flow meter to generate a base fluiddensity measurement; measuring a density of a fracture fluid with saidCoriolis flow meter to generate a fracture fluid density measurement,wherein said fracture fluid comprises a mixture of said base fluid and aproppant; and determining an amount of said proppant in said fracturefluid based on said base fluid density measurement, said fracture fluiddensity measurement, and said density of said proppant.
 13. The methodof claim 12 wherein the step of measuring a density of a fracture fluidwith said Coriolis flow meter comprises: measuring said density of saidfracture fluid with a straight tube Coriolis flow meter.
 14. The methodof claim 12 wherein the step of measuring a density of a fracture fluidwith said Coriolis flow meter comprises: receiving a slip stream of saidfracture fluid into said Coriolis flow meter to measure said density ofsaid fracture fluid.
 15. The method of claim 12 further comprising thesteps of: connecting a first end of a first tube to an input of saidCoriolis flow meter; connecting a second end of said first tube to adischarge of a tank; connecting a first end of a second tube to anoutput of said Coriolis flow meter; and connecting a second end of saidsecond tube to said tank; wherein said first tube receives a slip streamof material from said discharge of said tank, said slip stream travelsthrough said first tube, through said Coriolis flow meter, through saidsecond tube, and back into said tank.
 16. The method of claim 12 furthercomprising the step of: providing said amount of said proppant to auser.
 17. The method of claim 12 further comprising the step of:transmitting a signal representing said amount of said proppant to anauxiliary system.
 18. The method of claim 12 further comprising the stepof: receiving said density of said proppant from a user.
 19. The methodof claim 12 further comprising the steps of: calculating a velocity ofsaid fracture fluid; determining if said velocity of said fracture fluidexceeds a threshold; and providing an indication if said velocity ofsaid fracture fluid exceeds said threshold.
 20. The method of claim 12further comprising the steps of: calculating an average density of saidbase fluid based on a plurality of density measurements of said basefluid by said Coriolis flow meter; and determining said amount of saidproppant in said fracture fluid based on said average density of saidbase fluid, said fracture fluid density measurement, and said density ofsaid proppant.
 21. The method of claim 12 further comprising the stepsof: measuring a mass flow rate of said fracture fluid with said Coriolisflow meter; and providing at least one of said mass flow rate of saidfracture fluid and a drive gain of said Coriolis flow meter to a user.